Here's a full list of OSHA approved NRTL's:
Applied Research Laboratories, Inc. (ARL)
Canadian Standards Association (CSA)
(also known as CSA International)
Communication Certification Laboratory, Inc. (CCL)
Curtis-Straus LLC (CSL)
Electrical Reliability Services, Inc. (ERS)
(also known as eti Conformity Services and formerly Electro-Test, Inc. (ETI))
Entela, Inc. (ENT)
FM Approvals LLC (FM)
(formerly Factory Mutual Research Corporation)
Intertek Testing Services NA, Inc. (ITSNA)
(formerly ETL)
MET Laboratories, Inc. (MET)
NSF International (NSF)
National Technical Systems, Inc. (NTS)
SGS U.S. Testing Company, Inc. (SGSUS)
(formerly UST-CA)
Southwest Research Institute (SWRI)
TUV America, Inc. (TUVAM)
TUV Product Services GmbH (TUVPSG)
TUV Rheinland of North America, Inc. (TUV)
Underwriters Laboratories Inc. (UL)
Wyle Laboratories, Inc. (WL)